Expression of a nitrogen-fixation gene encoding a nitrogenase subunit in yeast

Area of Science:

• Molecular Biology
• Biochemistry
• Microbiology

Background:

• Biological nitrogen fixation is a crucial process catalyzed by the nitrogenase enzyme complex.
• Nitrogenase is exclusively found in prokaryotes, limiting its study in eukaryotic systems.
• Understanding nitrogenase component synthesis in eukaryotes could offer new avenues for nitrogen fixation research.

Purpose of the Study:

• To investigate the synthesis and assembly of nitrogenase components within a eukaryotic host, Saccharomyces cerevisiae.
• To express the Klebsiella pneumoniae nifH gene, encoding the Fe protein (Kp2) subunit, in yeast.
• To analyze the expression and characteristics of the prokaryotic nifH gene product in a eukaryotic cellular environment.

Main Methods:

• Expression of the Klebsiella pneumoniae nifH gene in Saccharomyces cerevisiae using the ADHI promoter.
• Detection of the nifH gene product (Kp2 subunit) in yeast via immunoblot analysis using specific antibodies.
• Assessment of protein electrophoretic mobility using SDS-polyacrylamide gel electrophoresis.
• Quantification of Kp2 antigen levels and beta-galactosidase activity from nifH'-'lacZ fusions.
• Comparison of gene expression under aerobic and anaerobic conditions and across different yeast strains and plasmids.

Main Results:

• The nifH gene product (Kp2 subunit) was successfully detected in yeast, exhibiting similar electrophoretic mobility to the native Kp2 subunit from K. pneumoniae.
• The level of nifH product expression in yeast was comparable under both aerobic and anaerobic growth conditions.
• Expression levels varied significantly depending on the transforming plasmids used and the specific haploid or diploid yeast strains employed.
• A downstream cistron within the nifHDKY operon transcript was found to be untranslated in the yeast system.

Conclusions:

• Saccharomyces cerevisiae can successfully synthesize the Fe protein (Kp2) subunit of nitrogenase from the Klebsiella pneumoniae nifH gene.
• This study demonstrates the feasibility of expressing prokaryotic nitrogenase components in a eukaryotic host.
• Further research is needed to understand the factors influencing expression levels and the potential for full nitrogenase complex assembly in eukaryotes.